System and Method For Applying A Coating To A Substrate

ABSTRACT

A process for providing a protective layer to an article. The process includes depositing a layer of material onto a surface of the article with a thermal spray process. Examples of thermal spray process include high velocity oxygen/air fuel, atmospheric plasma spray, and chemical vapor deposition. Coating methods, such as cold vapor deposition and physical vapor deposition, may also be used. The layer can then be bonded to the article by heating material in the layer adjacent its connection with the article. Bonding the layer to the article can be performed by irradiating the layer with a collimated light source, the layer irradiation can be applied concurrently with the thermal spray process

BACKGROUND

1. Field of Invention

The device described herein relates generally to a system and method of applying a coating onto a substrate. More specifically, the present disclosure relates to a system and method for applying a coating to a substrate using a thermal spray to deposit the coating and laser treatment of the deposited coating.

2. Description of Related Art

Structural materials subject to ambient conditions are typically treated to prolong their useful life. Treatment methods include forming the material from a corrosive resistant material, such as stainless steel, coating the material, or cladding the material. Coatings, such as paint or polymeric compounds, can protect a material from moisture and corrosive elements that can promote oxidation or galvanic action. However, most coatings wear over time and require replacing and if the protected component is a linkage member, the coating can be rubbed off with normal use. Therefore, to protect such members, a cladding may be required that is bonded to the member's outer surface and cannot be easily removed or eroded.

SUMMARY OF INVENTION

Disclosed herein is method of forming a bond between a body and an external layer. In an example the method includes providing a body having an external layer on an outer surface of the body, and heating the layer with collimated light so that particles in the layer are diffusion bonded to the surface. The method can include applying a thermal spray to the surface to deposit the layer thereon. The thermal spray can be applied by a high velocity oxygen fuel process or a high velocity air fuel process. Heating with collimated light can include directing a laser at the metallic layer. The steps of heating the layer with collimated light and depositing material onto the surface can be performed substantially in sequence. The method can further include applying a thermal spray to the heated and bonded metallic layer to deposit a second layer onto the surface, and heating the second metallic layer with collimated light so that particles in the second layer are bonded. The thermal spray can include a cobalt alloy powder. The cobalt alloy powder may include carbon; silicon; nickel; tantalum; nitrogen; manganese; chromium; molybdenum, cobalt, tungsten; iron, and combinations. The body can be a piston rod, the method further comprising installing the piston rod into a riser tensioning mechanism.

Alternatively disclosed herein is a method of sealing an article with a protective layer. In an example the method involves depositing a metal based layer of material onto a surface of the article using a thermal spray process and forming a diffusion bond between the metal based layer and the surface by heating the layer with collimated light. The method can also include regulating the metal based layer thickness so that the heat applied from the collimated light is transferrable through the layer to the interface between the layer and the surface. The step of depositing a metal based layer of material can implement a process such as high velocity oxygen fuel, high velocity air fuel, atmospheric plasma spray, cold spray, or physical vapor deposition. The article can be a portion of a riser tensioning device or ram tensioning device, where the method includes installing the article in the tensioning device. The article can be a piston rod.

In another method disclosed herein for protecting an article, the method can include depositing a metal based layer of material onto a surface of the article using a thermal spray process and simultaneously heating the layer with collimated light thereby forming a diffusion bond between the metal based layer and the surface.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side sectional view of a layer being deposited onto a substrate using a prior art thermal spray process;

FIG. 2 is a side cut-away view of a sample of a layer formed using a thermal spray process as shown in FIG. 1;

FIG. 3 is a side sectional view of a collimated light source heat treating a layer of deposited material, in accordance with an exemplary embodiment of the present technique;

FIG. 4 is a side cut-away view of a sample of a layer of deposited material treated as shown in FIG. 3;

FIG. 5 is a side sectional illustrating forming a layer using a thermal spray system, and simultaneously treating the layer using a collimated light source heat, in accordance with an exemplary embodiment of the present technique;

FIG. 6 is a side cut-away view of a sample of a layer of deposited and treated material treated as shown in FIG. 5;

FIG. 7 is a side cut-away view of a sample of a layer of deposited and treated material treated as shown in FIG. 5;

FIG. 8 provides a graph charting elemental presence in the sample with respect to distance from the layer surface;

FIG. 9 is an elevation view of a riser tensioner system, in accordance with an exemplary embodiment of the present technique; and

FIG. 10 is an elevation view of an exemplary embodiment of a ram tensioner piston rod having a coating applied and treated in accordance with the techniques described above.

While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

Objects can be protected with a coating applied using a thermal spray process; examples of which include, high velocity oxygen fuel (HVOF), high velocity air fuel (HVAF), atmospheric plasma spray, and plasma spray (in air or in low pressure atmospheres). Other coating methods that may be employed include cold spray and physical vapor deposition. In a side schematic view in FIG. 1, a thermal spray depositor 10 is shown forming a metal coating 12 onto a substrate 14. The spray depositor 10 includes a combustion chamber 16 at its upper end having feeds for oxygen, metal powder, and fuel. Oxygen connects to the combustion chamber 16 through an oxygen inlet 18, powder is provided to the chamber 16 through a powder inlet 20, and fuel through a fuel inlet 22. Combusting the fuel and oxygen within the combustion chamber 16 forms a jet stream that exits the chamber 16 and travels through a nozzle 24 attached to the combustion chamber 16. The jet stream exits the spray depositor 10, shown as a spray stream 26, where it is then deposited onto the substrate 14 for forming a coating 12 onto the substrate 14. The coating 12 can protect the substrate 14 from environmental conditions that can corrode, oxidize, erode, or otherwise degrade the material forming the substrate 14.

One of the shortcomings of a protective coating applied with a thermal spray process is that the coating 12 is not metallurgically bonded with the substrate 14. Additionally, gaps or porosities 28 may be present in the coating 12, which form an inconsistent coating 12 and potential crack initiation sites. FIG. 2 provides an image of a sample body having a coating 12 formed onto a substrate 14 by a thermal spray process; where porosities 28 are clearly present in the coating 12.

FIG. 3 illustrates a side sectional view of a coating 12 deposited on a substrate 14 with a thermal spray process being treated with a collimated light source 30. In one example of use, the collimated light source 30 is a laser. As shown, the light source 30 directs a beam 32 to the coating 12 upper surface. The energy in the beam 32 heats the coating 12 and provides a treating effect onto the coating 12 when sufficient heat over time is applied to the coating 12. Heat treating the coating 12 creates a treated area 34 having an increased density over untreated areas. Heat treating the layer can also form a diffusion bond 38 between a portion of the coating 12 and substrate 14.

Irradiating the coating 12 with the collimated light beam 32 can sufficiently heat the coating 12 to form a metallurgical bond to the substrate 14. The metallurgical bond can be an interdiffusion of elements from the coating 12 and the substrate 14. This is known as a diffusion bond 38. A particle to particle metallurgical bond can also be formed. Accordingly treating a coating 12 with a collimated light beam 32 can treat and densify a coating 12 and form a metallurgical bond 33 between the coating 12 and substrate 14. Creating a metallurgical bond between the coating 12 and substrate 14 ensures adhesion of the coating 12 to the substrate 14 and enhances the protective qualities of the coating 12.

It has been discovered, however, that the presence of the porosities 28 within a coating 12 being treated with a collimated light source 30 can coalesce the porosities 28 into a void or bubble space 36. The absence of material in a void or bubble space 36 reduces layer strength and therefore is not a desirable condition. FIG. 4 is a sectional image of a sample treated with a collimated light source. A treated zone 34 is shown extending along the upper portion of the coating 12. Also illustrated is a bubble zone 36 shown formed adjacent the treated area 34.

In FIG. 5, another example of forming a protective layer on an article is depicted in a side schematic view. In this embodiment, the collimated light source 30 is used to treat a layer of coating 12 as it is deposited on the substrate 14 by the thermal spray process device 10, or shortly thereafter while the coating 12 is still warm. As discussed above, irradiating the coating 12 with the collimated light beam 32 can sufficiently heat the coating 12 to form a diffusion bond 38 to the substrate 14. Accordingly treating the layer of the coating 12 with a collimated light beam 32 as the layer is applied can treat and densify the coating 12 to form a diffusion bond 38 between the coating 12 and substrate 14. As noted above, bonding the coating 12 and substrate 14 ensures coating 12 adhesion to enhance protective qualities of the coating 12.

Alternatives of operation with both the spray deposition device 10 and light source 30 exist wherein an entire area may optionally be coated with a deposit of material and then at a later time be treated with the beam 32 of the laser or light source 30. Optionally, incremental segments of the coating 12 can be formed, such as by the spray deposition device 10, and then treated with the light source 30. It is within the capabilities of those skilled in the art to determine the proper amount of heating in order to form a dispersion bond between the coating 12 and substrate 14. FIG. 6 illustrates a cutaway of a sample of a treated layer 34 having an increased density and wherein the layer 34 is fused to its associated substrate 14.

FIG. 7 provides a cutaway of a sample and having distance markers noted that identify a preset depth from the treated layer 34 upper surface and to a point beneath the substrate 14. In one example of use, the layer is formed from a cobalt-based metallic powdered mixture that includes chromium, nickel and cobalt. FIG. 8 depicts results of an elemental analysis of the layer 34 and substrate 14 of FIG. 7. As shown on the abscissa, is a representation of distance from the upper surface of the layer 34 and into the substrate 14. The ordinate represents an amount of the particular elements described at that location in the sample. It should also be pointed out that in the example the substrate 14 included an iron-based metal composition. Proximate to the depth noted as X μm, it is seen that the detection of chromium, nickel, and cobalt drops in a substantially infinite slope. In contrast, the detection of iron increases at a similarly but oppositely directed slope at X μm. This indicates the boundary between the treating layer 34 and the substrate 14, but also indicates that these elements within the grade deposition powder material have diffused into the substrate 14 by virtue of the laser treating process described above.

By creating a diffusion bond 38 between the treated layer 34 and the substrate 14, a protective barrier is provided onto the substrate material that is essentially an extension of the material itself. Therefore, the treated layer 34 is not likely to delaminate as is the case in some other protective coatings. Accordingly, the chances of caustic materials becoming imbedded between the layer and substrate are essentially eliminated. The method described herein can form a diffusion layer between the coating and the substrate with a thickness of about 2-3 μm. The diffusion layer formed is thinner than one formed using a convention cladding process, which can have a thickness in excess of 100 μm. The presence of a thin inter-diffusion layer also indicates low Fe dissolution into the coating layer and consequently preventing corrosion resistance deterioration due to high Fe content at the coating surface.

In one example of use, a protective layer is deposited with the thermal spray process onto a surface of a body to be protected. The thermal spray process uses a powder having carbon from about 0.06% to about 0.15% by weight of the metal mixture, chromium from about 26% to about 28% by weight of the metal mixture, cobalt from about 20% to about 54% by weight of the metal mixture, iron from about 2% to about 3% by weight of the metal mixture, manganese from about 0.8% to about 1% by weight of the metal mixture, molybdenum from about 5% to about 5.5% by weight of the metal mixture, nickel from about 9% 10% by weight of the metal mixture, nitrogen from about 0.15% to about 0.08% by weight of the metal mixture, silicon from about 0.3% to about 1% by weight of the metal mixture, and tungsten from about 2% to about 4.5% by weight of the metal mixture.

The article being treated and/or protected may be a part of a system used for producing hydrocarbons from a subsea wellhead. In one example, the article is included in a riser tensioning device used in a subsea well. The riser tensioning device can be what is referred to in the art as a “pull-up” type of a “push-up” type. With reference now to FIG. 9, an example of a tensioning mechanism 40 is shown in a side view. A riser 42 extends downwardly from a platform 44 to a subsea wellhead (not shown). Riser 42 has a longitudinal axis 46 and is surrounded by a plurality of hydraulic cylinders 48. Each hydraulic cylinder 48 has a cylinder housing 50 having a chamber (not shown). A piston rod 52 has a rod end 54 that extends downward from each cylinder housing 50 and hydraulic cylinder 48. The piston ends of rods 52 opposite rod ends 54 are disposed within the respective chambers (not shown) of cylinder housings 50. Hydraulic fluid (not shown) is contained within the housing 50 for pulling piston rods 52 upward. Each hydraulic cylinder 48 also has accumulator 56 for accumulating hydraulic fluid from hydraulic cylinder 48 and for maintaining high pressure on the hydraulic fluid. A riser collar 58 rigidly connects to riser 42. The piston rods 52 attach to riser collar 58 at the rod ends 54. Cylinder shackles 60 rigidly connect cylinder housings 50 to platform 44. In a specific example of use, the treating method described herein is used to protect a piston rod, such as the piston rod 52 of FIG. 9.

In another embodiment, a cladding method disclosed herein can be applied to a ram tensioner piston rod. An example of a hydro-pneumatic tensioner unit 128 is provided in a side view in FIG. 10. On the tensioner unit 128 upper end is a rod end cap 146 used for connection to a top plate (not shown) to provide tension to a riser system. The rod end cap 146 is shown as threadingly attached to a shoulder or flange 148 formed of or attached to the main body of a tensioner piston rod 132; bolts 150 are shown coupling the cap 146 and rod 132. In an embodiment, the lower end of the tension unit 128 is connected to the operational marine platform (not shown). The tensioner piston rod 132 reciprocates in a housing 130 in response to movement of the operational platform.

It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims. 

1. A method of forming a bond comprising: (a) providing a body having an external layer on a surface of the body; and (b) heating the layer with collimated light so that particles in the layer are diffusion bonded to the surface.
 2. The method of claim 1, further comprising applying a thermal spray to the surface to deposit the layer thereon.
 3. The method of claim 2, wherein the thermal spray is applied by a process selected from the list consisting of a high velocity oxygen fuel process and high velocity air fuel process.
 4. The method of claim 1, wherein step (b) includes directing a laser at the metallic layer.
 5. The method of claim 2, wherein the steps of heating the layer with collimated light and depositing material onto the surface are performed substantially in sequence.
 6. The method of claim 2, further comprising applying a thermal spray to the heated and bonded metallic layer to deposit a second layer onto the surface, and heating the second metallic layer with collimated light so that particles in the second layer are bonded.
 7. The method of claim 2, wherein the thermal spray includes a cobalt alloy powder.
 8. The method of claim 7, wherein the cobalt alloy powder includes carbon; silicon; nickel; tantalum; nitrogen; manganese; chromium; molybdenum, cobalt, tungsten; and iron.
 9. The method of claim 1, wherein the body comprises a piston rod, the method further comprising installing the piston rod into a tensioning mechanism.
 10. A method of sealing an article with a protective layer, the method comprising: depositing a metal based layer of material onto a surface of the article using a thermal spray process; and forming a diffusion bond between the metal based layer and the surface by heating the layer with collimated light.
 11. The method of claim 10, further comprising regulating the metal based layer thickness so that the heat applied from the collimated light is transferrable through the layer to the interface between the layer and the surface.
 12. The method of claim 10, wherein the step of depositing a metal based layer of material comprises using a process selected from the list consisting of high velocity oxygen fuel, high velocity air fuel, atmospheric plasma spray, cold spray, and physical vapor deposition.
 13. The method of claim 10, wherein the article comprises a portion of a riser tensioning device, the method further comprising installing the article in the tensioning device.
 14. A method of protecting an article comprising: (a) depositing a metal based layer of material onto a surface of the article using a thermal spray process; and (b) simultaneously with step (a), heating the layer with collimated light thereby forming a diffusion bond between the metal based layer and the surface. 